Ipg and header combination

ABSTRACT

A surgical lead is provided which includes a generally flexible polymeric panel incorporating a set of electrode arrays embedded in one side. The electrode arrays are connected to integrally formed leads which house conductors that connect the electrodes to a set of contacts. The contacts engage an IPG header. The leads incorporate an optical fiber which extends from the IPG header to a set of window portals in the flexible panel. Each of the fibers includes a side firing section adjacent the optical windows for transmission or reception of light. Optimally placed reflectors and heat shields are also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority benefits from U.S. ProvisionalApplication No. 62/869,372 filed on Jul. 1, 2019; U.S. ProvisionalApplication No. 62/869,377 filed on Jul. 1, 2019 and U.S. ProvisionalApplication No. 62/869,391 filed on Jul. 1, 2019. The patentapplications identified above are incorporated here by reference in itsentirety to provide continuity of disclosure.

FIELD OF THE INVENTION

The present invention relates to an improved implantable pulse generator(IPG) and header combination for using optical reflectometry in spinalcord stimulation (SCS).

BACKGROUND OF THE INVENTION

Chronic pain may arise from a variety of conditions, most notably fromnerve injury as in the case of neuropathic pain, or from chronicstimulation of mechanical nociceptors such as with spinal pain.Functional ability may be severely impacted by pain, which often isrefractory to pharmacological and surgical treatment. In such cases,spinal cord stimulation (“SCS”) can be an effective treatment for painby modulating physiological transmission of pain signals from theperiphery to the brain. This may be achieved by applying electricalimpulses to the spinal cord via an electrode array implanted adjacentthe spinal canal.

Spinal cord stimulator (SCS) system electrode leads may be classified aseither “percutaneous leads” or “surgical leads”. Percutaneous leadarrays contain multiple cylindrical electrode contacts which arearranged colinear along a thin cylindrical cable which is introducedinto the body via a needle. In contradistinction, surgical leads aregenerally comprised of an array of electrode contacts which protrude onone side from a thin lead body composed of a flexible substrate which isdirectly placed in the dorsal epidural space via a surgical laminotomy.

In FIG. 1, spinal column 1 is shown to have a number of vertebrae,categorized into four sections or types: lumbar vertebrae 2, thoracicvertebrae 3, cervical vertebrae 4 and sacral vertebrae 5. Cervicalvertebrae 4 include the 1st cervical vertebra (C1) through the 7thcervical vertebra (C7). Just below the 7th cervical vertebra is thefirst of twelve thoracic vertebrae 3 including the 1st thoracic vertebra(T1) through the 12th thoracic vertebra (T12). Just below the 12ththoracic vertebrae 3, are five lumbar vertebrae 2 including the 1stlumbar vertebra (L1) through the 5th lumbar vertebra (L5), the 5thlumbar vertebra being attached to sacral vertebrae 5 (S1 to S5), sacralvertebrae 5 being naturally fused together in the adult.

In FIG. 2, representative vertebra 10, a thoracic vertebra, is shown tohave a number of notable features which are in general shared withlumbar vertebrae 2 and cervical vertebrae 4. The thick oval segment ofbone forming the anterior aspect of vertebra 10 is vertebral body 12.Vertebral body 12 is attached to bony vertebral arch 13 through whichspinal nerves 11 run. Vertebral arch 13, forming the posterior ofvertebra 10, is comprised of two pedicles 14, which are short stoutprocesses that extend from the sides of vertebral body 12 and bilaterallaminae 15. The broad flat plates that project from pedicles 14 join ina triangle to form a hollow archway, spinal canal 16. Spinous process 17protrudes from the junction of bilateral laminae 15. Transverseprocesses 18 project from the junction of pedicles 14 and bilaterallaminae 15. The structures of the vertebral arch protect spinal cord 20and spinal nerves 11 that run through the spinal canal.

Surrounding spinal cord 20 is dura 21 that contains cerebrospinal fluid(CSF) 22. Epidural space 24 is the space within the spinal canal lyingoutside the dura.

Referring to FIGS. 1, 2 and 3, the placement of an electrode array forspinal cord stimulation according to the prior art is shown. Electrodearray 30 is positioned in epidural space 24 between dura 21 and thewalls of spinal canal 16 towards the dorsal aspect of the spinal canalnearest bilateral laminae 15 and spinous process 17.

FIG. 4 shows a prior art surgical electrode array 30 including electrodecontacts 35 sealed into elastomeric housing 36. Electrode array 30 haselectrode leads 31 which are connected to electrical pulse generator 32and controller 33. Each electrode contact has a separate electricalconductor in electrode leads 31 so that the current to each contact maybe independently controlled.

Spinal cord stimulators often include an implantable pulse generator(IPG) 32 which monitors and delivers the electrical stimulation to thespinal cord through the electrode array 31. The IPG is typicallycontained in a titanium canister which is implanted subcutaneously nearthe upper buttocks or flank and draws power from a battery. Theelectrode array is connected to the IPG using subcutaneous leads.

The subcutaneous leads interface with electrode contacts located in theheader of an IPG. Typically, the leads are secured in the IPG with ananchor screw.

The IPG delivers pulses of electrical current to the electrode array,which travel through the electrodes to targeted neurons within theascending tracts of the spinal cord. The resulting electric fielddisrupts the perception of pain. Controlling the amplitude of thestimulating electrical field is paramount to success of spinal cordstimulation. Applying inadequate current will fail to depolarize thetargeted neurons, rendering the treatment ineffective. Conversely,application of excess current will depolarize the targeted neurons, butalso stimulate additional cell populations which renders the perceptionof a noxious stimulation.

Establishing a consistent, therapeutic, and non-noxious level ofstimulation is predicated upon establishing an ideal current densitywithin the spinal cord's targeted neurons. Fundamentally, this should bea simple matter of establishing an optimal electrode current given thelocal bulk conductivity of the surrounding tissues. But in practice, theoptimal electrode current changes as a function of patient position andactivity due to motion of the spinal cord as the spinal cord floats incerebrospinal fluid within the spinal canal. Significant changes indistance between the epidural electrode array and the targeted spinalcord neurons have been shown to occur. Consequently, optimal stimulationrequires dynamic adjustment of the electrode stimulating current as afunction of distance between the electrode array and the spinal cord.

Dynamic modulation of spinal cord stimulator electrode current as afunction of distance between the electrode array and the spinal cordthus has several benefits. Excess stimulation current can be avoided,thus reducing the prospects of noxious stimulation and potentiallyreducing device power consumption. Inadequate stimulation current canalso be avoided, thus eliminating periods of compromised therapeuticefficacy.

Dynamic modulation of electrode current can be controlled through theuse of optical reflectometry to determine the thickness of the dorsalcerebrospinal fluid (dCSF) column between the spinal cord and theelectrode array. An optical signal is transmitted into the surroundingtissue and collected by a sensor to calculate the approximate distancebetween the electrode and the spinal cord. The stimulus magnitude ismodified accordingly to provide the optimal current for pain relief. Anexample of this technology is shown in U.S. Pat. No. 10,035,019 to WolfII, incorporated herein by reference.

One challenge to subcutaneous IPG implants is the long-term survival ofthe IPG in the harsh in vivo environment. Functional and mechanicaldegradation may occur with the ingress of body fluids. Proteins commonin the blood and interstitial fluid are known to bind to metallic ions,leading to corrosion. Some materials can trigger an immune response andpotentially a change in the local pH balance of the implantation site.Specialized polymers and epoxies can avoid some of these problems, butoften exhibit unacceptably high levels of cytotoxicity. Consequently, itis imperative to maintain the IPG internal components in a hermeticallysealed environment and that the external IPG components bebiocompatible.

Similarly, another challenge to subcutaneous IPG implants is thetendency for the surrounding tissue to degrade around the IPG due toincreased pressure the IPG edges place on the tissue. Erosion of thedevice through the skin can occur, typically at the corners of thedevice where there is a focal concentration of pressure, and requiresrevision surgery to replace the device.

Another challenge to implementation of optical reflectometry foradaptive spinal cord stimulation is that leads coupled imprecisely tothe IPG header are susceptible to movement which interferes with thestability of the optical signal. Unstable optical signals result inundesirable signal-to-noise ratio which results in errors in deliveredcurrent and imprecise stimulation.

Yet another challenge to subcutaneous IPG implants is the extendedrecharge times. IPGs including a rechargeable battery must beperiodically recharged. Electromagnetic induction has evolved as themost widely used technology for recharging IPG batteries. However,during recharging, eddy currents are produced in the IPG casing causingtemperature increase. To maintain an acceptable temperature, chargingduty cycles are typically shorter than ideal, thereby increasing thetime required for recharging.

The prior art has attempted to address these challenges in a number ofways.

For example, U.S. Pat. No. 6,011,993 to Tziviskos, et al. describes amethod of making a strong ceramic case that can house electronics with agood hermetic seal for implantation into the body. However, Tziviskosdoes not describe how to effectively connect or secure electrical leadsor optical fibers.

As another example, U.S. Pat. No. 6,324,428 to Weinberg, et al.describes a medical implant that contains the internal electronics in apreferred configuration that minimizes the volume of the implant, makingit easier to implant. However, Weinberg does not describe any designfeature that reduces device erosion, nor does it disclose how to coupleelectrical leads or optical fibers to the implant.

Similarly, U.S. Pat. No. 7,742,817 to Malinowski, et al. describes anIPG with connectors for electrical leads and an epoxy coating forbiocompatibility. However, Malinowski does not disclose the use ofoptics in the design to achieve proper pulse strength.

Deficiencies exist in the prior art related to the accuracy of leadcoupling when using optical reflectometry for spinal cord stimulation.Thus, there is a need in the art for an improved IPG case, connectors,leads and electrodes which provide a stable optical signal whileoptimizing the longevity of the IPG.

BRIEF DESCRIPTION OF THE DRAWINGS

In the detailed description of the preferred embodiments presentedbelow, reference is made to the accompanying drawings.

FIG. 1 is a side view of the human spine showing the approximateposition of an electrode array for spinal cord stimulation.

FIG. 2 shows an axial view of a thoracic vertebra indicating theposition of the spinal cord and an electrode array for spinal cordstimulation.

FIG. 3 shows a sagittal cross-sectional view of the human spine showingthe approximate position of an electrode array for spinal cordstimulation.

FIG. 4 shows a prior art surgical electrode array and lead connector forspinal cord stimulation.

FIG. 5 shows a schematic of an IPG charging and communication system ofa preferred embodiment.

FIG. 6A is an isometric view of a preferred IPG device.

FIG. 6B is a cross-sectional top view of a preferred IPG shapedemonstrating a super ellipse curve.

FIG. 6C is a cross-sectional front view of a preferred IPG shapedemonstrating a super ellipse curve.

FIG. 6D is cross-sectional side view of a preferred IPG shapedemonstrating a super ellipse curve.

FIG. 6E is an isometric view of a preferred IPG shape demonstrating asuper ellipse curve.

FIG. 6F is an exploded isometric view of a preferred IPG device.

FIG. 7A is a side view of a header for a preferred IPG device.

FIG. 7B is a cross-sectional top view of a header for a preferred IPGdevice.

FIG. 7C is a detail view a preferred header for an improved IPG device.

FIG. 7D is a top view of a preferred header bay for an improved IPGdevice.

FIG. 7E is a rear view of a header for an improved IPG device.

FIG. 8 is a cross-sectional view of a preferred IPG body.

FIG. 9A is a plan view of an optical window for an improved IPG device.

FIG. 9B is a cross-sectional side view of an optical window for animproved IPG device.

FIG. 10A is a plan view of an optical window for an improved IPG device.

FIG. 10B is a cross-sectional side view of an optical window for animproved IPG device.

FIG. 11A is a plan view of an optical window for an improved IPG device.

FIG. 11B is a cross-sectional side view of an optical window for animproved IPG device.

FIG. 11C is an isometric view of an optical window for an improved IPGdevice.

FIG. 11D is an isometric view of an optical window for an improved IPGdevice.

FIG. 12A is a front view of a preferred daughterboard for an improvedIPG device.

FIG. 12B is a rear view of a preferred daughterboard for an improved IPGdevice.

FIG. 12C is an isometric view of a preferred daughterboard for animproved IPG device.

FIG. 12D is a schematic of an optical signal for an improved IPG device.

FIG. 12E is a graphical depiction of the advantages of a leadconfiguration.

FIG. 12F is a method diagram for calculating stimulation.

FIG. 12G is a front view of a daughterboard for an improved IPG device.

FIG. 12H is a rear view of a daughterboard for an improved IPG device.

FIG. 12I is an isometric view of a daughterboard for an improved IPGdevice.

FIG. 12J is a schematic of an optical signal for an improved IPG device.

FIG. 13A is a side view of a preferred embodiment of subcutaneous leads.

FIG. 13B is a cross-sectional view of a preferred embodiment ofsubcutaneous leads.

FIG. 13C is a cross-sectional view of an alternative embodiment ofsubcutaneous leads.

FIG. 13D is an exploded side view of an optical fiber and ferruleconfiguration.

FIG. 13E is a side view of a preferred embodiment of an optical fiberand ferrule assembly.

FIG. 13F is an exploded side view of an optical fiber and colletassembly.

FIG. 13G is a side view of a preferred embodiment of an optical fiberand collet assembly.

FIG. 13H is an exploded side view of a lead assembly.

FIG. 13I is a plan view of an optical fiber threading assembly.

FIG. 13J is a plan view of an optical fiber threading assembly.

FIG. 13K is an exploded perspective view of an optical fiber threadingassembly.

FIG. 14A is a plan view of a preferred surgical lead.

FIG. 14B is a cross-sectional view of a preferred surgical lead.

FIG. 14C is a cross-sectional view of a preferred surgical lead.

FIG. 15A is a plan view of a preferred surgical lead.

FIG. 15B is a cross-sectional view of a preferred surgical lead.

FIG. 16A is a plan view of a surgical lead.

FIG. 16B is a cross-sectional view of a surgical lead.

FIG. 16C is an isometric view of a parabolic reflector for a surgicallead.

FIG. 17A is a plan view of a surgical lead.

FIG. 17B is a cross-sectional view of a surgical lead.

FIG. 18 is flowchart of the steps of a preferred method of placement ofa surgical lead.

FIG. 19 is flowchart of the steps of a preferred method of placement ofa percutaneous lead.

FIG. 20 is flowchart of a method of the steps of a preferred method ofsecuring an optical fiber in a stylet channel of a lead.

DETAILED DESCRIPTION OF THE INVENTION

In the description that follows, like parts are marked throughout thespecification and figures with the same numerals, respectively. Thefigures are not necessarily drawn to scale and may be shown inexaggerated or generalized form in the interest of clarity andconciseness.

Referring then to FIG. 5, IPG charging and communication system 500comprises an IPG device 510 implanted subcutaneously beneath skinsurface 530.

IPG device 510 comprises an external non-metallic case 507 whichfacilitates transmission of charging and communication signals, withexternal system manager 516, as will be further described.

IPG device 510 further comprises main processor 505, operativelyconnected to signal processor 509. Main processor 505 is furtheroperatively connected to secondary coil 511 and RF antenna 532, as willbe further described.

Signal processor 509 is operatively connected to optoelectrical devices503, as will be further described.

Optoelectrical devices 503 are positioned to send and receive light intoand out of, respectively, leads 512 of surgical lead 514, as will befurther described.

Main processor 505 is further operatively connected to battery 533,secondary coil 511 and RF antenna 532. In use, main processor 505mitigates charging battery 533 from current induced in secondary coil511, by primary coil 518, as will be further described. Main processor505 further receives signals from RF antenna 532, for use incommunicating data regarding operation of the IPG device, as will befurther described.

The system further comprises external system manager 516. Externalsystem manager 516 includes external processor 520, operativelyconnected to primary coil 518 and RF antenna 534.

In use, external processor 520 includes a set of instructions whichcontrol a charging signal sent to primary coil 518. In use, primary coil518 is placed physically near secondary coil 511 and activated. Theactivation of the primary coil induces a current in the secondary coilwhich is routed to the battery by the main processor for charging thebattery. The activation of the primary coil and the inductive chargingof the battery can be continuous since there are no eddy currentscreated in the non-metallic case. A continuous charging duty cycle foran IPG is a significant improvement over the prior art which reduces IPGcharging time.

RF antenna 534 is used to send and receive signals to RF antenna 532 toreceive information and control operation of IPG device 510, as will befurther described.

Referring then to FIG. 6A, IPG device 501 comprises IPG body 506 andheader 502. Leads 504 are removably secured in the header, as will befurther described.

Referring then to FIGS. 6B, 6C, 6D and 6E, the preferred shape for IPGdevice 501 will be described. In general, the preferred shape of the IPGcase is defined by two (2) unique super ellipse equations, one for eachof the side and top perspectives. The case is symmetrical about eachprincipal axis. The external shape of the IPG case is important becausea near Gaussian distribution of curvatures over the surface greatlyreduces the risk of erosion of the case through the skin afterimplantation of the IPG device, thereby increasing the survivability ofthe surgical implant. The preferred super ellipse equations which definethe shape of the case are preferably Lame curve equations.

The device three-dimensional shape is a volume of revolution havingprinciple axes x, y and z. The volume of revolution is symmetrical abouteach principle axis. Referring to FIG. 6C, from the front, in the x yplane, the volume of revolution is preferably a circle, defined by theequation:

$\begin{matrix}{{{\frac{a}{2}}^{2} + {\frac{b}{2}}^{2}} = r^{2}} & {{Eq}.\mspace{14mu} 1}\end{matrix}$

where:

-   -   a=width along the x axis;    -   b=height along the y axis;    -   r=radius.        Typical values for a and b are about 50 mm. A typical value for        r is about 25 mm.

Referring to FIG. 6D, from the side, in the y z plane the volume ofrevolution is preferably a super-ellipse defined by the equation:

$\begin{matrix}{{{\frac{z}{c}}^{n} + {\frac{y}{b}}^{n}} = 1} & {{Eq}.\mspace{14mu} 2}\end{matrix}$

where:

-   -   b=height along the y axis;    -   c=depth along the z axis;    -   n is between about 1.5 and about 5, and is preferably about 2.        A typical value for b is about 50 mm. A typical value for c is        about 12 mm.

In one preferred embodiment, the super ellipse in the y z plane isrotated about the z axis to obtain the volume of revolution.

Referring to FIG. 6B, from a top, in the x z plane, the volume ofrevolution is preferably a super-ellipse defined by the equation.

$\begin{matrix}{{{\frac{x}{a}}^{n} + {\frac{z}{c}}^{n}} = 1} & {{Eq}.\mspace{14mu} 3}\end{matrix}$

where:

-   -   a=width along the x axis;    -   c=depth along the z axis;        A typical value for a, is about 50 mm. A typical value for c, is        about 12 mm.

Referring then to FIG. 6F, an exploded view of improved IPG device 600will be described.

IPG device 600 is comprised of header 602 and IPG body 606. IPG body 606is further comprised of IPG casing 622, optical window 618 andelectrical feedthrough plate 616. IPG casing 622 is formed by twoopposing shell halves, 622 a and 622 b, hermetically sealed at junction620. In a preferred embodiment, IPG casing 802 is a ceramic material,such as alumina, sapphire or zirconia. In another embodiment, the IPGcasing may be formed of a molded amorphous glass, such as Pyrex®. Inalternative embodiments, the IPG casing may be comprised of titanium oran alloy. In a preferred embodiment, ceramic brazing with inducedwelding is applied at the junction of the casing halves. Other processesmay be used to join the halves.

The header is fixed in header bay 619 by a suitable medical gradepermanent adhesive, as will be further described.

Optical window 618 is preferably a crystal insert in a wall of theheader bay that is hermetically sealed in the IPG casing, as will befurther described. Alternatively, in embodiments where the IPG casing isformed of an optically transparent material, optical window 618 may takethe form of a pair of polished surfaces integrally formed in the headerbay wall, of the IPG casing, adjacent the header body.

Leads 604 are removably coupled with header 602 and secured in placeusing anchor screws 614 or 615, as will be further described.

Referring then to FIG. 7A, header 700 is comprised of header body 701.The header body is preferably formed of a cast rigid non-metallicmaterial of sufficient strength to support radial forces from the anchorscrews, such as methyl PMMA or polyester reinforced with fiberglass orgraphite fibers. The header body includes a plurality of generallylatitudinal and parallel lead channels, such as lead channel 702. In apreferred embodiment, the header body includes four lead channels.Alternatively, it may have two lead channels. Each lead channel, such aslead channel 702 is generally cylindrical and includes a lead channelaxis, such as axis 719, which forms an optical axis for the lead, aswhich will be further described.

Each lead channel includes eight annular connector bays such asconnector bay 703, formed inline on the interior of each channel.Connector bays 703 are equally spaced along the channel axis of eachlead channel. Each connector bay houses a canted coil connector spring,such as canted coil spring 704. Each canted coil connector spring is ahelical metallic coil which forms a toroid and which is spring loaded toexert an internally directed radial bias against a metallic leadconnector, as will be further described. Preferably, the canted coilsprings are platinum alloy to assure failsafe electrical and mechanicalcontact with the lead contacts. In a preferred embodiment, the cantedcoil springs are Bal Conn® for Neuromodulation available from B al-SealEngineering of Foothill Ranch, Calif. Each of the canted coil springs isconnected to one connector pin, such as connector pin 706, located atthe base of the header.

Header body 701 includes a set of horizontal threaded holes,perpendicular to the lead channels, such as threaded hole 732, adjacentthe IPG casing, extending from the exterior of the header body to thelead channel. An anchor screw, such as anchor screw 708, is located ineach threaded hole.

In a preferred embodiment, the threaded holes are tapped or castdirectly into the header body or alternatively cast into the IPG casing.This configuration is important because it eliminates the need for aseparate anchoring block in the header and conserves space byincorporating these components into the IPG casing. Furthermore,placement of the anchoring screw nearest the proximal end of the leadchannel provides a secure mechanical connection of the lead closest tothe optical components, promoting a stable optical signal.

Optionally, the header body may further comprise an integrally formedanchor block 799. In this embodiment, the threaded holes and anchorscrews are resident in the anchor block adjacent the optical window. Theanchor block is preferably a medically inert metal such as titaniummolded into the header body.

Referring then to FIG. 7B, threaded hole 732 houses anchor screw 708.Diametrically opposed to threaded hole 732 is threaded hole 707.Threaded hole 707 houses anchor screw 705.

Referring then to FIG. 7C, frustoconical centering surface 724 isadjacent to and coaxial with lead channel 702. Frustoconical centeringsurface 724 centers the lead on the optical axis of the lead channel asit is inserted into the lead channel. The frustoconical centeringsurface is adjacent anchor ring chamber 728. The anchor ring chamber isbounded by cylindrical alignment surface 726 and is coaxial with thefrustoconical centering surface. The anchor ring chamber is also boundedby stop surface 730. Stop surface 730 is an annular ring at the proximalend of the anchor ring chamber. The stop surface is coaxial with theanchor ring chamber. In use, stop surface 730 abuts the proximal end ofthe lead body and prevents it from being inserted past the desired pointin lead channel 702 during assembly. Each of these surfaces is importantfor accurate positioning of the lead and the optical fiber and promotesefficient and accurate optical signal transfer.

Anchor screw 708 engages the lead anchor ring in the anchor ring chamberwhen the IPG is assembled. In the case where the threaded holes areformed in the header body, the anchor screw is installed with a torquelimited driver to prevent excess force from being placed on the header.In the case where the header body includes an anchor block, the anchorblock allows sufficient axial force to be applied by the anchor screw tothe anchor ring to hold it securely in place, without fracturing theheader body.

The lead channel is further comprised of ferrule chamber 727 bounded byalignment cylinder 712. The ferrule chamber is coaxial with the leadchannel.

Ferrule centering surface 716 is adjacent to and coaxial with alignmentcylinder 712 and is designed to hold the ferrule and the optical fiberin optical alignment with the optical axis of the lead channel.Alignment cylinder 712 forms chamfer angle θ, with ferrule centeringsurface 716. In a preferred embodiment, chamfer angle θ can range fromabout 135° to about 150°, ±5°. Ferrule centering surface 716 centers andaligns the proximal end of the lead and optical ferrule with buffer gap734, optical window 718 and composite optoelectronic device 740.

Cylindrical buffer surface 714 is adjacent to and coaxial with ferrulecentering surface 716. Cylindrical buffer surface 714 forms buffer gap734 between the proximal end of the optical ferrule and optical window718. The buffer gap prevents application of pressure to the opticalwindow from fluid or tissue build up on the ferrule tip or fromirregularities of the optical fiber polished surface at the ferrule tip.

Referring then to FIG. 7D, electrical feedthrough plate 616 comprises aflat insulator, preferably a ceramic material, and is fixed at thebottom of header bay 619 by a suitable adhesive, or by ceramic welding.Electrical feedthrough plate 616 is comprised of a plurality ofreceivers, such as receiver 746. The receivers are connected to the maincircuit board, as will be further described. Connector pins 706 at thebase of the header body interface with the receivers.

Referring then to FIG. 7E, in a preferred embodiment, the header iscomprised of four lead channels 702, 709, 713, and 717. Each leadchannel includes a perpendicularly oriented threaded hole 732, 707, 733and 739 and anchor screws 708, 705, 711 and 715, respectively.

In the prior art, there is typically an anchor ring, which is engaged bya set-screw to fix the lead contacts within the header. The anchor ringis typically placed distal to the contacts, requiring a separateanchoring block to engage the lead and set-screw. One advantage of thisembodiment is that the anchor ring may be positioned proximal to thelead contacts, nearest the end of the lead. This positioning eliminatesthe need for a separate anchoring block and reduces the size of the IPGcasing if threaded holes 732, 707, 733, and 739 are integrated into theheader body as may be achieved through injection molding of a ceramic orglass. Further, placement of the anchoring ring nearest the proximal tipof the lead provides mechanical fixation of the lead closest to theoptical components, promoting a stable optical signal.

Referring then to FIG. 8, IPG body 800 is further comprised of IPGcasing 802, optical window 806, electrical feedthrough plate 804,composite optoelectronic device 816, connector card 812, main circuitboard 818, battery 808, and capacitor 810.

The electrical components are secured in the casing with appropriateinsulated plastic standoffs, such as standoffs 820 and 821.

Electrical feedthrough plate 804 is hermetically sealed to IPG casing802, adjacent the header bay. The electrical feedthrough plate ismechanically fixed to connector card 812 and is connected to maincircuit board 818 by flexible ribbon cable 805.

Optical window 806 is hermetically sealed to the IPG casing in aposition perpendicular to both the electrical feedthrough plate and thelead channels. In a preferred embodiment, optical window 806 iscomprised of synthetic sapphire. Synthetic sapphire provides optimaloptical properties for transmitting visible red or infrared lightbetween composite optoelectronic device 816 and optical transmissionfibers, as will be further described.

Composite optoelectronic device 816 is positioned adjacent the opticalwindow and held in position parallel to the optical window by thedaughterboard. The optoelectronic device 816 is also perpendicular tothe optical axis of the lead channels. Daughterboard 814 is furthercomprised of processor 803, as will be further described. Daughterboard814 is held in position by the standoffs and is connected to maincircuit board 818 by ribbon cable 807. The ribbon cable supplies powerto the daughterboard and communicates control signals as required.

Main circuit board 818 is positioned in the IPG casing by the standoffsand is operatively connected to the battery, the capacitor, the contactsof the leads and the daughterboard.

Main circuit board 818 receives data input from the daughterboard andgenerates stimulation pulses which vary in frequency, pulse-width, andamplitude based on signals from the daughterboard. The stimulationpulses are sent to the lead contacts for transmission to the electrodes.The daughterboard generates control signals for the main circuit boardby sending light pulses from the light emitters and receiving andinterpreting signals from light detectors, as will be further described.The main circuit board is also operatively connected to secondaryinduction coil 809 and RF antenna 811.

The main circuit board includes processors and radio signal generatorswhich allow it to communicate signals to exterior receiving devicesthrough RF antenna 811. In a preferred embodiment, the main processorand the RF antenna are used to communicate a warning signal from thedaughterboard if an emitter current reaches a maximum value, as will befurther described.

Capacitor 810 is connected to battery 808 and stores energy from thebattery to produce the stimulation pulses. In a preferred embodiment,battery 808 is a lithium-ion rechargeable battery. Battery 808 isinductively charged through secondary induction coil 809 positionedaround the battery on one internal surface of the IPG casing. The maincircuit board controls the recharging duty cycle.

Referring then to FIGS. 9A and 9B, in a preferred embodiment, opticalwindow 900 is a polished rectangle single crystal alumina (sapphire) orpolycrystalline alumina ceramic. It is joined to IPG case 901 in theheader bay by ceramic brazing. Niobium is used as a metal to ceramicfiller material. In a preferred embodiment the alumina is 94% brazed toFe-29Ni-10Co internally at approximately 1000° C. Optical window 900 isbrazed to IPG case 901 along window braze junction 906 using hermeticbraze fillet 904. In FIG. 9B, optical window 900 and IPG case 901 areshown as coplanar, but these may alternatively be stacked or overlaid.

Referring then to FIGS. 10A and 10B, in another embodiment, opticalwindow 1000 is overlaid on the outside of IPG case 1001, adjacent theheader bay. In this embodiment, IPG case 1001 includes four (4)waveguides 1008. The waveguides are holes in the header bay wall thatallow red or infrared light to be transmitted through the opticalwindow, along the optical axis of each lead channel and into theinterior of the IPG casing. Optical window 1000 is hermetically sealedto IPG case using brazing, soldering, epoxy or other suitable meansalong window junction 1006.

Referring then to FIGS. 11A, 11B, 11C and 11D, in another preferredembodiment, window plate 1104 comprises a flat sapphire rectangle about1 mm thick. Four optical wave guides, 1106 are fused to the window plateusing ceramic welding. In another embodiment, the window plate andoptical waveguides are integrally formed from the same crystalstructure. Each optical wave guide includes an internally reflectiveiris 1108. The iris is a cylindrical hole which is concentricallyaligned with the optical axis of a lead channel. Window plate 1104 islaser welded to IPG casing 1101 along weld joint 1102.

When assembled, each of the optical wave guides passes through holes1110 and into the interior of the IPG casing. In a preferred embodiment,each optical wave guide abuts an optoelectronic device on thedaughterboard secured in the IPG casing, as previously described. Inpractice, the iris is important because it prevents light loss betweenthe optical fiber in the lead and the optoelectronic devices.

Referring then to FIGS. 12A, 12B, and 12C, daughterboard 814 ispreferably a 2-sided PC board supporting optoelectronic devices 1204,1205, 1206, and 1207, connector 1210, and processor 1208. Processor 1208draws power from the battery and is supplied with an onboard memory thatcontains instructions for its operation. The optoelectrical devices arepositioned in quadrants adjacent the proximal surface of the opticalwindow. Each quadrant is separated by an optical opaque light baffle1212. In a preferred embodiment, the baffle is a “cross-shaped” PVCstandoff, approximately 1-2 mm in height, coated with a reflectivelayer, such as TiO₂, on its exterior surface and bonded to thedaughterboard with a suitable adhesive. Each of the optoelectronicdevices is positioned to be perpendicular to and aligned with theoptical axis of one lead channel in order to maximize eithertransmission or reception of light from an optical fiber, positioned inthe lead channel. In a preferred embodiment, optoelectronic devices1204, 1205, 1206, and 1207 and light baffle 1212 may be integrated intoone or more application specific integrated circuits (ASIC s).

Connector 1210 links daughterboard 814 to the main circuit board of theIPG device. Processor 1208 is electrically connected to theoptoelectronic devices through the daughterboard as required tocommunicate electrical signals to the processor.

In one embodiment, optoelectronic device 1204 is an optical emitter andoptoelectronic devices 1205, 1206, and 1207 are optical detectors.

In another embodiment, optoelectronic devices 1204, and 1206 are opticalemitters and optoelectronic devices 1205, and 1207 are opticaldetectors.

The wavelengths of the emitters may range from visible red to infrared,or approximately 620-1700 nanometers. The emitter(s) may be eithersingle wavelength or multiple wavelengths. For instance, the emittercould be a high-speed, single wavelength infrared emitting diode of 850nm wavelength, such as part no. VSMY1850 available from VishayIntertechnology, Inc. of Malvern, Pa. Alternatively, the emitter couldbe a multi-chip emitter, such as product no. MTMD6788594SMT6 availablefrom Marktech Optoelectronics, Inc., of Latham, N.Y., which is capableof emitting wavelengths 670 nm, 770 nm, 810 nm, 850 nm, and 950 nm.Alternatively, an emitter and detector may be integrated into a singleASIC such as with the ADPD144RI from Analog Devices, Inc. of Norwood,Mass.

Referring to FIG. 12D, a preferred embodiment of a coupling arrangementbetween optical leads and optical emitters in a surgical lead will bedescribed. Emitter 1292 is optically coupled to central fiber 1215 ofsurgical lead 1211. Detector 1290 is optically coupled to lead 1213 ofsurgical lead 1211. Detectors 1294 and 1296 are connected to leads 1217and 1219, respectively.

Referring to FIG. 12E, a graph showing light output from a side firingfiber of a surgical lead and input current to a corresponding emitterover time, will be described.

Light output over time is shown by the curve labeled “a”. It can be seenthat the light output of fiber 1215 degrades over time due tomicrofractures in the fiber and other degradation of optical componentsin the surgical lead. The decrease in optical performance of fiber 1215is monitored over time by processor 1208 by reading the voltage signalfrom detector 1296, which receives light from fiber 1215 reflected bythe spinal cord. Processor 1208 is programmed to compensate for thedegradation in light output by increasing the current to emitter 1204according to curve “b”. As can be seen, increasing the current toemitter 1204 maintains the light output of fiber 1215 at a consistentlevel shown by curve “c” as shown in the drawing.

Referring to FIG. 12F, a self-adjusting emitter current program foradjusting light output from an emitter fiber will be described. In apreferred embodiment, the program is a series of instructions thatreside in the memory of processor 1208.

At step 1262, the program begins.

At step 1264, the processor sets the output current to emitter 1292. Ina preferred embodiment, the emitter current is set to the minimumrequirement to generate a readable signal at detectors 1290 and 1296.

At step 1266, the processor reads the voltage at detector 1294. At step1268, the voltage level is stored in memory. At step 1270, processor1208 sends a signal to main circuit board 818 to initiate a stimulationprogram. The main circuit board responds by sending appropriatestimulation signals to the leads.

At step 1272, processor 1208 determines whether or not a self-timer hasexpired. If so, the program proceeds to step 1274. If not, the programreturns to step 1270.

At step 1274, processor 1208 reads the detector voltage at detector1294.

At step 1276, the processor compares the present value detector voltageto the stored detector voltage in memory. If the present value detectorvoltage is less than the stored detector voltage, then the process movesto step 1278. If not, the program returns to step 1270.

At step 1278, processor 1208 increases the emitter current to emitter1204. In a preferred embodiment, the emitter current is increased by1/100 of the maximum emitter current permitted.

At step 1280, the processor determines whether or not the emittercurrent is set to the maximum allowed. If so, the program moves to step1282. If not, the program returns to step 1274.

At step 1282, the processor sends a signal to the main circuit board,which communicates it through the RF antenna to an external receiver,indicating that the maximum emitter current has been reached. Theprogram then returns to step 1270.

Referring then to FIGS. 12G, 12H, and 12I alternate embodiment ofdaughterboard 814 will be further described.

Daughterboard 1201 is a composite optoelectrical device comprised ofoptoelectronic devices 1250, and 1252, connector 1254, and signalprocessor 1209. The optoelectrical devices are positioned adjacent andparallel to the optical window. In a preferred embodiment, eachoptoelectronic device is separated by an optical opaque light baffle1251. In a preferred embodiment, baffle 1251 is a reflective or opaquerectangular PVC standoff bonded to the daughterboard, as previouslydescribed.

Connector 1254 links daughterboard 1201 to the main circuit board of theIPG device. Processor 1209 is electrically connected to theoptoelectronic devices through the daughterboard as required andcommunicates external signals to the signal processor. The daughterboardcommunicates to the main circuit board through connector 1254.

Referring then to FIG. 12J, a preferred embodiment of a couplingarrangement between optical leads and optical emitters in a surgicallead will be described. Emitter 1293 is optically coupled to centralfiber 1225 of signal lead 1221. Detector 1291 is optically coupled tolead 1223 of signal lead 1221. Emitter 1295 is optically coupled tocentral fiber 1227 and detector 1297 is connected to lead 1229. In thisconfiguration, dual optical reflectometry channels facilitate thestereoscopic detection of spinal cord position in the sagittal andcoronal planes as previously described in U.S. Pat. Nos. 8,239,038;8,543,213; 9,132,273; 9,656,097 to Wolf II, incorporated herein byreference.

Referring to FIGS. 13A-13G, a preferred embodiment of percutaneous lead1400 is described.

Referring then to FIGS. 13A and 13B, in a preferred embodiment of leadbody 1402 is comprised of a generally hollow tube terminated bytransmission window 1409. In a preferred embodiment, the lead body iscomprised of a flexible polymer such as Pellethane 55-D, or similarbiocompatible polymer. The lead body is preferably a multi-lumenextrusion available from Zeus Industrial Products, Inc. of Orangeburg,S.C.

Transmission window 1409 is a hollow cylinder fused to the terminus ofthe flexible lead body enclosing diffuser cavity 1430. In a preferredembodiment, the window is a suitable optically transparent material suchas thermoplastic polyurethane. Transmission window 1409 is terminated bycap 1425. Cap 1425 includes internally reflective surface 1403 whichfaces into diffuser cavity 1430. In a preferred embodiment, theinternally reflective surface is a titanium dioxide coating.

Stylet channel 1405 extends from the transmission window to the proximalend of the lead body. The stylet channel serves the dual purposes ofhousing a guide stylet for use during placement of the lead duringsurgery, and housing and optical fiber after surgery, as will be furtherdescribed. In a preferred embodiment, stylet channel 1405 is lined withpolytetrafluoroethylene (PTFE) lining 1407 which extends from the lengthof the lead body up to transmission window 1409. The extremely lowsurface friction afforded by the carbon-fluorine bonds of the PTFEfacilitates manual insertion of the stylet and the optical fiber. Thelining does not extend into the diffuser cavity, where the side-firingsegment of the optical transmission fiber resides, to enhance opticaltransmission.

Metallic anchor ring 1410 is positioned at the proximal end of the leadbody. The anchor ring is generally cylindrical and is permanentlyaffixed to the exterior of the lead body proximal to the lead contacts.Eight cylindrical proximal metallic contacts 1408 a, 1408 b, 1408 c,1408 d, 1408 e, 1408 f, 1408 g, 1408 h are fixed to the exterior of thelead body at even axial distances along the lead body and positioned toelectrically contact the coil springs in the header.

In the same way, eight cylindrical distal metallic electrodes 1406 a,1406 b, 1406 c, 1406 d, 1406 e, 1406 f, 1406 g, 1406 h are provided atthe distal end of the lead body. The distal lead contacts are each andpermanently fixed to the exterior surface of the lead. The distal leadcontacts are evenly spaced along the lead body proximal to the opticalwindow.

The lead body further comprises eight radially oriented lumens 1431 a,1431 b, 1431 c, 1431 d, 1431 e, 1431 f, 1431 g and 1431 h. Conductors1420 a, 1420 b, 1420 c, 1420 d, 1420 e, 1420 f, 1420 g, 1420 h arelocated in the lumens and extend from respective proximal contacts todistal electrodes. In a preferred embodiment the conductors arecomprised of MP35N, or another conductive material similarly resistantto corrosion. Each of the conductors connects exactly one proximalcontact to a single paired distal electrode.

Referring then to FIG. 13C, a cross-sectional view of an alternateembodiment of lead body 1450, is described.

Lead body 1450 comprises nine radially oriented lumens, 1449 a, 1449 b,1449 c, 1449 d, 1449 e, 1449 f, 1449 g, 1449 h and 1449 i. Conductors1451 a, 1451 b, 1451 c, 1451 d, 1451 e, 1451 f, 1451 g and 1451 h andground line 1451 i are located in the lumens. Ground line 1451 i extendsfrom the proximal end of the lead body to the transmission window.Ground line 1451 i is electrically connected to anchor ring 1410. Whenthe anchor screw engages anchor ring 1410, the ground lead is connecteddirectly to the IPG ground either through the anchor block or through aground connection through the header. The ground line may be used tosupplement electrical shielding of the electrode array contacts forbetter MRI compatibility.

In another preferred embodiment, the lead body may incorporatenon-metallic shielding layer 1496, connected to ground line 1451 i, tofurther enhance MRI capability. In a preferred embodiment, the shieldinglayer is formed by carbon fibers infused into the surface of the leadbody. In another preferred embodiment, low friction layer 1493, such asPTFE, is included on the exterior of the lead body to aid in placementof the lead during surgery.

Referring then to FIGS. 13D and 13E, optical fiber subassembly 1419includes ferrule 1412 and optical fiber 1418.

Ferrule 1412 is generally a ceramic cylinder. Ferrule 1412 includesintegrally formed alignment tip 1413. Alignment tip 1413 is a chamferformed in the ferrule with a chamfer angle of θ, preferably is betweenabout 135° and 150°. In a preferred embodiment, chamfer angle θ matchesthe chamfer angle 735 of centering surface 716, so that when the ferruleis mounted in the header there is an elastic compression of the ferruleby the polymer lead body. When mounted, the positive stop of the ferruleby ferrule centering surface 716 prevents pressure being applied tosealed optical window 718 by the fiber or the ferrule. Hole 1415 iscentered in ferrule 1412 and extends through the length of the ferrule.In a preferred embodiment, the diameter of the hole closely matches thediameter of the optical fiber. In a preferred embodiment, ferrule 1412is made of a polished ceramic, preferably zirconia, or other MRIcompatible material.

Ferrule 1412 is positioned at the proximal end of optical fiber 1418.Optical fiber 1418 includes end reflector 1414 and side-firing fibersegment 1416 at its distal end and polished optical tip 1411 at itsproximal end. Optical fiber 1418 is preferably comprised of apolymethylmethacrylate core with a fluorocarbon cladding of about250-400 micrometers in diameter. In a preferred embodiment, the fiberalso includes a low friction layer 1447, preferably comprised of PTFE.In use, the low friction layer aids in insertion of the fiber in thestylet lumen.

Optical fiber 1418 includes reflector 1414 at its distal end. Thereflector prevents axial light emission from the fiber and improvesradial dispersion of light. The reflector thereby improves opticalsignal strength and lowers power consumption. Ideally, the reflector iscomprised of a titanium dioxide layer coated on the end of the fiberafter it has been thermally polished.

Side-firing fiber segment 1416 is positioned in diffuser cavity 1430,adjacent cap 1425, and is typically about 5 mm in length. Side-firingfiber segment 1416 is formed by modification of the cladding of theoptical fiber. The cladding may be modified by using femtosecond laseretching, mechanical abrasion, or an alternative method to achieve radialleakage of light.

Polished optical tip 1411 is positioned at the proximal end of theoptical fiber. Polished optical tip 1411 is preferably a thermallypolished surface perpendicular to the optical axis of the fiber.Optionally, a convex lens may be attached to the proximal end of thefiber to focus light into or out of the fiber, as will be furtherdescribed.

Referring then to FIG. 13E, optical fiber subassembly 1419 is positionedin stylet channel 1405. The outer diameter of ferrule 1412 is less thanthe outer diameter of lead body 1402 but greater than the diameter ofstylet channel 1405, such that the lead body acts as a stop for theferrule.

In one embodiment, optical fiber subassembly 1419 is placed in thestylet channel after surgical placement of the lead body in vivo, aswill be further described.

In another embodiment, the fiber subassembly is prefabricated into thelead body. In this embodiment, the proximal end of the optical fiber issecured to the fiber by a suitable adhesive. One such suitable medicalgrade adhesive is preferably an optically transparent biocompatibleepoxy seal, such as EPO-TEK® MED-353ND by Epoxy Technology, Inc. ofBillerica, Mass. In this case, polished optical tip 1411 is polishedflush with alignment tip 1413.

Referring then to FIG. 13F, an alternate embodiment of optical fibersubassembly 1419 will be described.

Lead body 1401 includes stylet channel 1405 having an optical axis 1421.The lead body incorporates proximal contacts, distal electrodes andelectrical conductors, as previously described. Stylet channel 1405 isterminated with frustoconical flare 1482. Frustoconical flare 1482 iscoaxial with optical axis 1421. The frustoconical flare has inclinationangle β, which can range from about 135° to about 150°.

In a preferred embodiment, the lead channel has a diameter of about15-20% greater than the optical fiber to allow the fiber to move withinthe channel. Optical fiber 1444 is preferably a plastic fiber, aspreviously described. Optical fiber 1444 includes end reflector 1446 andside-firing fiber segment 1445, as previously described.

Optical fiber 1444 is proximally terminated by convex lens 1452. Convexlens 1452 consists of a polished ceramic material, such as sapphire,fixed to the optical fiber using a suitable optically transparentadhesive. In another embodiment, the lens is formed integrally with thetransmission fiber. In another embodiment, the optical fiber is polishedflat and no lens is incorporated.

Collet 1457 includes collet body 1453. Preferably, collet body 1453 iscomprised of a ceramic material, such as Zirconia, or another MRIcompatible material. Alignment tip 1454 is a chamfer integrally formedin the distal end of the collet body. Alignment tip 1454 forms angle ofinclination γ of about 135°. In a preferred embodiment, angle γ matchesangle θ of frustoconical flare 1482.

Collet body 1453 further includes cylindrical collet chamber 1456.Collet chamber 1456 is coaxial with collet body 1453 and extends throughalignment tip 1454. In a preferred embodiment, the collet is bonded tooptical fiber 1444 at the collet chamber.

Lens shield 1469 is integrally formed with the proximal end of colletbody 1453. It is designed to serve as a stop to prevent the opticalfiber from impinging on the optical window of the IPG body. Lens shield1469 further includes frustoconical lens opening 1468 ductedly connectedwith collet chamber 1456. The frustoconical lens opening is coaxial withthe collet chamber and has an angle of inclination δ of about 175° withthe collet chamber. Frustoconical lens opening 1468 serves to focuslight toward the optical window.

Referring then to FIG. 13G, the proximal end of the optical fiber isshown positioned in collet chamber 1456. Lens 1452 does not extend pastlens shield 1469. The fiber is fixed in the collet chamber by a suitableepoxy.

Optical fiber 1418 is positioned in stylet channel 1405 of lead body1401. Frustoconical flare 1482 serves to guide insertion of the opticalfiber into the lead channel. The interface of frustoconical flare 1482and alignment tip 1454 also serves to center optical fiber 1444 and lens1452 on axis 1421. The outer diameter of collet 1457 is less than theouter diameter of lead body 1401 but greater than the diameter of styletchannel 1405, such that when the lead is inserted in the header, thelead body acts as a stop for the collet, such that the side firing fibersegment of the fiber is adjacent the optical window.

Referring then to FIG. 13H-13K, a preferred embodiment of opticalthreading assembly 1460 is described. Inserting the optical fiber intothe stylet channel of the lead can be difficult due to the miniaturesize of the fiber and small diameter of the stylet channel. In the sameway, during surgery, the replacement of the stylet in the stylet channelcan be difficult. These difficulties are compounded by necessity forspeed, manual dexterity and visual acuity. Improper insertion of theoptical fiber can lead to damage to the fiber causing breakage or earlydegradation of the fiber. Likewise, improper stylet insertion cancompromise the lead body. The optical fiber threading assembly solvesthese and other problems.

Optical threading assembly 1460 includes guide body 1497. The guide bodyis a roughly 1 cm diameter cylinder and is comprised of thermoplastic.The assembly is preferably formed either using injection molding, oradditive manufacturing. Other methods of manufacture will suffice. Guidebody 1497 is generally cylindrical and is comprised of two opposingsemicylinders, 1461 and 1462.

Optical threading assembly 1460 includes frustoconical lead centeringsurface 1463 at its distal end. Frustoconical lead centering surface1463 is coaxial with axis 1421. Frustoconical lead centering surface1463 is adjacent cylindrical alignment surface 1467. Cylindricalalignment surface 1467 forms alignment cavity 1498. Frustoconical leadcentering surface 1463 forms an angle of inclination τ of about 135°with cylindrical alignment surface 1467. The alignment cavity has adiameter generally equal to that of lead body 1402. The alignment cavityis terminated with stop surface 1466. Stop surface 1466 is a generallyannular ring formed perpendicular to and coaxial with axis 1421.

Adjacent to and ductedly connected with alignment cavity 1498, isgenerally cylindrical fiber alignment duct 1499. Fiber alignment duct1499 is coaxial with axis 1421. The diameter of the fiber alignment ductis generally the same as the diameter of stylet channel 1405 of leadbody 1402.

Fiber alignment duct 1499 is adjacent to and ductedly connected withfrustoconical optical fiber centering surface 1465. Frustoconicaloptical fiber centering surface 1465 forms an angle of inclination η ofabout 135° with fiber alignment duct 1499. Frustoconical optical fibercentering surface 1465 is coaxial with axis 1421.

Semicylinder 1461 includes alignment pegs 1474, 1470, and 1472.Semicylinder 1462 includes alignment recesses 1475, 1471, and 1473.Alignment peg 1474 is diametrically opposed to alignment recess 1475.Alignment peg 1470 is diametrically opposed to alignment recess 1471.Alignment peg 1472 is diametrically opposed to alignment recess 1473.The diameter of each of alignment recesses 1475, 1471, and 1473 is suchthat alignment pegs 1474, 1470, and 1472 can be secured by a press fit.Using the alignment pegs and recesses, the semicylinders may be easilyassembled for use and then disassembled after use, as will be furtherdescribed.

In use, optical threading assembly 1460 aligns lead body 1402 andoptical fiber subassembly 1419 along axis 1421. Lead body 1402 isaligned using frustoconical lead centering surface 1463 and held inposition in alignment cavity 1498 by alignment surface 1467 and stopsurface 1466. Optical fiber subassembly 1419 is aligned usingfrustoconical centering surface 1465 and moved through fiber alignmentduct 1499 and into the stylet channel of the lead body.

In the same way, a stylet may be positioned in the stylet channel inplace of the optical fiber.

Referring then to FIGS. 14A-15B, alternate embodiments for surgicalleads are described.

Surgical leads may be configured with two or more multi-duct leadscontaining integrated optical fibers, depending upon the number ofelectrodes in the array and the desired number of optical reflectometrychannels. The multi-duct leads may be organized into pairs of emitterleads and detector leads. Generally, a surgical lead configured with twomulti-duct leads incorporate one optical reflectometry channel, while asurgical lead with four multi-duct leads incorporates two opticalreflectometry channels. A surgical lead with two multi-duct leads withintegrated optical fibers is capable of determining sagittal spinal cordposition. Whereas a surgical lead with four multi-duct leads withintegrated optical fibers is capable of determining sagittal and coronalspinal cord position.

Referring then to FIG. 14A, a preferred embodiment of surgical lead 1500is described.

Electrode array 1500 is comprised of integrated flexible panel 1502.Panel 1502 is preferably of a medical grade inert polymer material, suchas Pellethane 55-D. Flexible panel 1502 houses multi-duct leads 1506,1510, 1514, and 1518. In a preferred embodiment, the multi-duct leadsare sealed within the body of the flexible panel. Each of multi-ductleads 1506, 1510, 1514, and 1518 includes a central lumen 1595, 1596,1597 and 1598, respectively. Each central lumen includes an opticaltransmission fiber 1541, 1543 1545 and 1547, respectively. Each opticaltransmission fiber terminates at a distal end in a side firing opticalfiber segment, 1535, 1536, 1537 and 1538, respectively. The side firingoptical fiber segments are constructed, as previously described. Eachside firing optical fiber segment is positioned adjacent distallypositioned optical window 1533, 1532, 1531 and 1530, respectively. In apreferred embodiment, each of the optical windows is an opticallytransparent segment of the polymer comprising flexible panel 1502. Byplacing the optical windows and the side firing segment at the mostdistal portion of the panel, there are no metallic components such aselectrodes or connections to interfere with radial dispersion of light,while keeping the optical sensing region proximate the electrode arrays.This improves optical signal strength and consequently lowers powerconsumption. In an alternate embodiment, the optical windows are placedparallel to and adjacent columns of the electrode arrays.

Panel 1502 further comprises electrode arrays 1504, 1508, 1512, and 1516positioned adjacent multi-duct leads 1506, 1510, 1514 and 1518,respectively. In a preferred embodiment, each of electrode arrays 1504,1508, 1512, and 1516 include eight electrodes embedded in the panel andhaving an exposed face external to the panel. Each of multi-duct leads1506, 1510, 1514 and 1518 incorporate eight electrical conductors thatextend the length of the panel and the multi-duct leads, as previouslydescribed. Each electrode is connected through the conductors in thelead body to exactly one lead contact. Electrode array 1504 is connectedto lead contacts 1507. Electrode array 1508 is connected to leadcontacts 1511. Electrode array 1512 is connected to lead contacts 1515.Electrode array 1516 is connected to lead contacts 1519. In a preferredembodiment, the electrodes are comprised of platinum-iridium alloy(nominally 90%/10% to 80%/20%).

Each of multi-duct leads 1506, 1510, 1514 and 1518 terminates atferrules 1505, 1509, 1513 and 1517, respectively. In a preferredembodiment, the ferrules are bonded to the fibers, as previouslydescribed.

Referring then to FIGS. 14B and 14C, each of electrode arrays 1504,1508, 1512 and 1516 is connected through electrical connections 1519,1521, 1523 and 1525 to one of conductor bundles 1540, 1542, 1544 and1546, respectively. The conductor bundles contain the individualconductors, radially separated, as previously described. The side firingfiber segments separate from the multi-duct leads and away from theconductor bundles in manifolds 1580, 1581, 1582 and 1583, respectively.

Panel 1502 includes light reflectors 1550, 1551, 1552 and 1553, adjacentside firing optical fiber segments 1535, 1536, 1537, and 1538,respectively. The light reflectors are preferably semicylindrical orparabolic, and flexible. In a preferred embodiment, light reflectors1550, 1551, 1552 and 1553 are comprised of a non-conductive materialpolymer, such as Pellethane-55D, coated with a non-conductive reflectivesurface, such as titanium dioxide. This material operates at the desiredwavelength from red to infrared and may be applied as a paint or film.The reflections improve optical efficiency by redirecting radiallyproduced light from the emitter fiber segments toward the opticalwindows, or, alternatively, reflecting incoming light from the opticalwindows and into the detector fiber segments.

Panel 1502 is further comprised of lattice shield 1526. Lattice shield1526 is comprised of a generally flat flexible film and interdigitateswith the polymeric material of the lead body. In a preferred embodiment,lattice shield 1526 is coated with a reflective material, such astitanium dioxide (TiO₂) adjacent the optical fibers. Lattice shield iscontained within the panel adjacent each of conductor bundles 1540,1542, 1544 and 1546, and generally extends the length of the panel.

In one embodiment, the lattice shield may be comprised of anelectrically conductive material, such as carbon nanofibers, andoperates as a heat-sink to draw heat away from the electrode contactarrays and disperse it dorsally. In another embodiment, leads 1518,1514, 1510, and 1506 each include a ground, as shown in FIG. 13C. Groundline 1451 i connects lattice shield 1526 with the anchor ring located atthe proximal end of the lead. The anchor ring is connected to the IPGground. This configuration provides optimal electrical shielding for MRIcompatibility.

Referring then to FIG. 15A, a preferred embodiment of surgical lead 1600is described.

Surgical lead 1600 is comprised of integrated flexible panel 1602. In apreferred embodiment, flexible panel 1602, is a medical grade inertflexible polymeric material, as previously described. Integrated withinthe flexible panel are multi-duct leads 1608 and 1610. Each ofmulti-duct leads 1608 and 1610 includes central lumen 1698 and 1699,respectively. The central lumens include optical fibers 1611 and 1612,respectively. Each optical fiber terminates in a side firing opticalfiber segment 1618 and 1619, respectively. The side firing opticalsegments are constructed as previously described. Each side firingoptical segment is positioned adjacent an optical window 1621 and 1620,respectively. In a preferred embodiment, each of the optical windows isan integrally formed optically transparent region of flexible panel1602.

Panel 1602 further comprises electrode arrays 1604 and 1606. Each ofelectrode arrays 1604 and 1606 includes eight electrodes, embedded inthe surface of panel 1602, having an exposed face exterior to the panel.In a preferred embodiment, the electrodes are a platinum-iridium alloy.Each of the electrodes is connected through the conductors in themulti-duct lead bodies to exactly one lead contact, as previouslydescribed. Electrode array 1604 is connected to lead contacts 1630.Electrode array 1606 is connected to lead contacts 1632.

Each of multi-duct leads 1608 and 1610, terminates at ferrules 1690 and1691, respectively. The ferrules are attached and bonded to the opticalfibers, as previously described.

Referring then to FIG. 15B, the conductors in the multi-duct lead bodiesseparate from side firing optical fiber segment 1618 and 1619 in opticalmanifolds 1653 and 1652, respectively. Each of electrode arrays 1604 and1606 is connected through electrical connections 1650 and 1651 to theconductors in one of conductor bundles 1640 and 1642, respectively.

Panel 1602 is further comprised of lattice shield 1614. Lattice shield1614 is comprised of a generally flat flexible film that is integrallyformed with both the flexible panel. As previously described, thelattice shield may be coated with reflective material adjacent theoptical fibers. The lattice shield may be connected to a ground contactfor further connection to the IPG ground, as previously described.

Panel 1602 further comprise reflectors 1616 and 1625, positionedadjacent side firing optical fiber segments 1618 and 1619, respectively.In preferred embodiments, the reflectors are generally semicylindricalor are parabolic. In another embodiment, the reflectors may be flatflexible panels. The reflectors serve to aid in the reflection of lightemitted from a side firing fiber segment out through an optical windowor to focus incoming light through optical windows and back into thefiber for transmission to a detector within the IPG.

Referring to the FIGS. 16A, 16B and 16C, an alternate embodiment ofsurgical lead 1700 will be described. Integrated panel 1702 is generallyflat, polymeric and rectangular, as previously described. Integratedwithin integrated panel 1702 are multi-duct leads 1718, 1720 and 1722with optical fiber 1736, as previously described. Each of the multi-ductleads have proximal electrical contacts which are individually connectedto electrode arrays 1712, 1714 and 1716 through conductors, aspreviously described. Integrated panels 1702 further comprises opticalwindow 1709 integrated into the panel adjacent side firing fibersegments 1730, 1732 and 1734, as previously described.

Composite reflector 1710 is comprised a plurality of alternatingparabolic surfaces, such as parabolic surfaces 1750, 1752 and 1754, andflat interstitial surfaces such as surfaces 1756 and 1758. The parabolicsurfaces and the flat surfaces are preferably comprised of a flexibleinert plastic with sufficient rigidity to sustain moderate bending. In apreferred environment, polyvinyl chloride is used. Internal surfaces1751, 1753 and 1755 of the parabolic surfaces and internal surfaces 1757and 1759 of the flat surfaces all are coated with a reflective materialsuch as titanium dioxide. Internal surfaces 1751, 1753 and 1755 arepositioned adjacent side firing fiber segments 1730, 1732 and 1734 andserve to function as previously described.

In another preferred embodiment, composite reflector 1710 is grounded tothe IPG case, through a conductor in one of the multi-duct leads, aspreviously described.

Referring then to FIGS. 17A and 17B an alternate embodiment of surgicallead 1800 will be further described.

Integrated panel 1802 generally comprises a flat, polymeric andrectangular, as previously described. Integrated panel 1802 includeelectrode arrays 1810 and 1812 connected to multi-duct leads 1814 and1818, as previously described. Integrated panel 1802 further comprisemulti-duct leads 1814, 1816 and 1818 integrally formed, as previouslydescribed. Each of multi-duct leads 1814, 1816 and 1818 includes opticalfiber 1850 with side firing fiber segments 1820, 1822, and 1824. Eachoptical fiber 1850 is positioned to terminate in a right-angle prism,such as right-angle prism 1804, 1806, and 1808. The right-angle prismsare positioned to direct light to an optical fiber from optical windows1811, 1813, and 1817, or from the optical fiber to an optical window, asthe case may be.

Referring then to FIG. 18, method 1900 for the placement of a surgicallead, will be described.

At step 1902, a laminotomy is conducted at the segmental levelcorresponding to the somatotopic distribution of the patient's pain.

At step 1904, electrodes are placed in the spinal canal. Typically, theelectrodes are placed in the dorsal epidural space by manually insertingthe electrode array in the laminotomy cavity.

At step 1906, the electrodes are anchored to the fascia, ligament or theadjacent bone.

At step 1908, an incision is made for the IPG.

At step 1910 the leads are tunneled subcutaneously from the electrodeinsertion site to the IPG pocket.

At step 1914, the multi-duct leads are secured in the IPG header. If thefibers are not secured in the multi-duct leads, then they may beinserted and secured at this step, as will be further described. Inpractice, the lead body, including the fiber subassembly, is threadedinto the appropriate lead channel bringing the proximal lead contactsinto electrical contact with the canted coil springs, of the leadchannel. The multi-duct lead is advanced in the lead channel until themulti-duct lead body encounters frustoconical centering surface 724,which guides it along cylindrical alignment surface 726, until itengages stop surface 730 in anchor ring chamber 728. Simultaneously, theferrule is advanced into alignment cylinder 712 until it encountersferrule centering surface 716. Ferrule centering surface 716 aligns theoptical fiber in buffer gap 734 and with the optical window in the IPGcasing, adjacent the composite optoelectronic device 740. The multi-ductlead is secured in the lead channel by advancing anchor screw 708, usinga torque limited ratchet, until it engages anchor ring 1410.

At step 1916 the IPG is placed in the pocket.

At step 1918, the procedure is ended.

Referring to FIG. 19, preferred method 2000 of placement of apercutaneous lead will be described.

At step 2002, a Touhy needle and needle stylet are inserted into spinalcanal at the appropriate segmental level.

At step 2004, the needle stylet is removed from the lumen of the Touhyneedle.

At step 2006, the percutaneous lead with included stylet guide wire isinserted into the bore of the Touhy needle.

At step 2008, the percutaneous lead is guided to the proper location inthe spinal canal using the stylet guide wire, under fluoroscopy.

At step 2010, the stylet guide wire is removed from the stylet channel.

At step 2012, the optical fiber is inserted into the stylet channel, aspreviously described.

At step 2014, the Touhy needle is removed, while holding the lead inplace.

At step 2016, the proximal end of the percutaneous lead is secured inthe IPG header, as previously described.

Referring then to FIG. 20, step 2012 of securing the optical fiber in astylet channel of a lead, will be further described.

At step 2102, semicylinders 1461 and 1462, are aligned with thepercutaneous lead body. At step 2104, semicylinders 1461 and 1462 areassembled by press fit. At step 2106, the proximal end of thepercutaneous lead body is inserted into the alignment cavity of thethreading assembly, guided by frustoconical lead centering surface 1463.Alignment surface 1467 aligns the multi-duct lead body with alignmentcavity 1498.

At step 2108, optical fiber 1418 is inserted into fiber alignment duct1499, guided by frustoconical optical fiber centering surface 1465. Theoptical fiber is then inserted into stylet channel 1405 of multi-ductlead body 1402, of the threading assembly.

At step 2110, ferrule 1412 is threaded onto optical fiber 1418.

In an alternate embodiment, a stylet may be placed in the fiberalignment duct and the stylet channel at this step. If so, the methodconcludes here.

At step 2112, the threading assembly is disassembled.

At step 2114, the semicylinders are removed from the assembled lead bodyand optical fiber.

1. A percutaneous lead for a pulse generator comprising: a flexible leadbody, incorporating a stylet channel, and having an internal surface andan external surface, and having a distal end and a proximal end; anoptical transmission section, having an optical fiber diffuser cavity,at the distal end; a set of electrodes, positioned adjacent the opticaltransmission section, fixed to the external surface; an anchor ring,positioned at the proximal end, fixed to the external surface; a set ofcontacts, adjacent to the anchor ring; a set of conductors incorporatedinto the flexible lead body; wherein at least one contact, of the set ofcontacts, is electrically connected to at least one electrode of the setof electrodes by a conductor of the set of conductors; an optical fiber,terminated in a radial light dispersion section, positioned in thestylet channel; wherein the radial light dispersion section ispositioned in the optical fiber diffuser cavity; and, a cylindricalferrule, having a frustoconical centering surface, positioned on theoptical fiber.
 2. The percutaneous lead of claim 1 wherein the anchorring is positioned proximal to the set of contacts.
 3. The percutaneouslead of claim 1 further comprising: a low friction surface adjacent theinternal surface.
 4. The percutaneous lead of claim 1 furthercomprising: a low friction surface adjacent the external surface.
 5. Thepercutaneous lead of claim 3 wherein the low friction surface is apolytetrafluoroethylene material.
 6. The percutaneous lead of claim 1wherein the optical fiber further comprises a low friction exteriorsurface.
 7. The percutaneous lead of claim 1 wherein the optical fiberis removable from the stylet channel.
 8. The percutaneous lead of claim1 wherein the optical fiber further comprises a polymethylmethacrylatematerial.
 9. The percutaneous lead of claim 1 wherein the optical fiberincludes an internally reflective tip, adjacent the radial lightdispersion section.
 10. The percutaneous lead of claim 9 wherein theinternally reflective tip is further comprised of a non-metallicreflective coating.
 11. The percutaneous lead of claim 1 wherein the setof conductors is radially positioned in the lead body, between theinternal surface and the external surface.
 12. The percutaneous lead ofclaim 1 wherein: the flexible lead has a lead external diameter and astylet channel diameter; the ferrule has a ferrule exterior diameter;and, wherein the ferrule exterior diameter is greater than the styletchannel diameter and lesser than the lead exterior diameter.
 13. Thepercutaneous lead of claim 12 wherein the pulse generator furthercomprises: a housing; a header, adjacent the housing, having a leadchannel; an optical window, positioned in the housing, adjacent the leadchannel; the housing supporting a set of optical components adjacent theoptical window; the header further comprising a lead channel having anoptical axis; a frustoconical ferrule receiving surface, terminating thelead channel, adjacent optical window; and; wherein the frustoconicalcentering surface is positioned adjacent the frustoconical ferrulereceiving surface.
 14. The percutaneous lead of claim 13 wherein theheader further comprises: a radial anchor screw positioned in theheader, adjacent the anchor ring; and, wherein advancing the radialanchor screw anchors the lead body in the lead channel.
 15. Thepercutaneous lead of claim 14 wherein: the lead channel furthercomprises a plurality of toroidal header connections; and, at least onecontact of the set of contacts is in electrical contact with at leastone toroidal header connection of the plurality of header connections.16. A percutaneous lead for a pulse generator comprising: a flexiblelead body, incorporating a stylet channel, and having an internalsurface and an external surface, and having a distal end and a proximalend; an optical transmission section, having an optical fiber diffusercavity, at the distal end; a plurality of electrodes, positionedadjacent the optical transmission section, fixed to the externalsurface; an anchor ring, positioned at the proximal end, fixed to theexternal surface; a plurality of contacts, adjacent the anchor ring;wherein at least one contact of the plurality of contacts iselectrically connected to at least one electrode of the plurality ofelectrodes; an optical fiber, terminated in a radial light dispersionsection, positioned in the stylet channel; wherein the radial lightdispersion section is located in the optical fiber diffuser cavity; theoptical fiber further comprising a lens, positioned along a firstoptical axis; a cylindrical collet, having a distal chamfer, axiallypositioned on the optical fiber, adjacent the lens; a frustoconicalflare, axially positioned in the stylet channel at the proximal end,adjacent the distal chamfer; and, wherein the cylindrical colletpositions the lens to focus on the optical axis.
 17. A percutaneous leadthreading device comprising: a rigid body, having an alignment axis; afrustoconical optical fiber centering surface, at a proximal end of therigid body; a frustoconical lead centering surface, at a distal end ofthe rigid body, coaxial with the alignment axis; a cylindrical alignmentcavity, in the rigid body, adjacent and coaxial with the frustoconicallead centering surface; and, an alignment duct, in the rigid body,connecting the alignment cavity with the frustoconical fiber centeringsurface, and coaxial with the alignment axis.
 18. The device of claim 17wherein the rigid body is formed from a first semicylinder removablyjoined to a second semicylinder.
 19. The device of claim 17 wherein: thecylindrical alignment cavity is terminated in an annular stop surface,coaxial with the alignment axis; and, the percutaneous lead ispositioned adjacent the stop surface, thereby aligning the percutaneouslead with the alignment axis.
 20. The device of claim 19 furthercomprising: an optical fiber, resident in the alignment duct and thepercutaneous lead.
 21. The device of claim 19 further comprising: astylet resident in the alignment duct and the percutaneous lead.
 22. Amethod of threading a strand body into a stylet lumen of a percutaneouslead comprising: providing an alignment body, having a central axis;providing a frustoconical fiber centering surface in the alignment body,aligned with the central axis; providing a fiber alignment duct, in thealignment body, adjacent to the frustoconical fiber centering surfaceand coaxial with the alignment axis; providing a cylindrical alignmentcavity, in the alignment body, adjacent to and coaxial with the fiberalignment duct; providing a frustoconical lead centering surface, in thealignment body, adjacent to the cylindrical alignment cavity and coaxialwith the alignment axis; positioning the percutaneous lead in thealignment cavity adjacent the fiber alignment duct; centering the strandbody in the fiber alignment duct; and, inserting the strand body intothe stylet lumen.
 23. The method of claim 22 further comprising:providing the alignment body as a first semicylinder and a secondsemicylinder; assembling the first semicylinder with the secondsemicylinder prior to inserting the strand body; and, disassembling thefirst semicylinder from the second semicylinder after inserting thestrand body.
 24. The method of claim 22 further comprising: providingthe strand body as an optical fiber.
 25. The method of claim 22 furthercomprising: providing the strand body as a wire stylet.
 26. A method ofinstalling a percutaneous lead, having a style channel, in a spinalcanal comprising: positioning the percutaneous lead using a cannulatedTouhy needle; inserting a stylet wire into the stylet channel; guidingthe percutaneous lead to a final position using the stylet wire;anchoring the percutaneous lead; withdrawing the stylet wire; and,inserting a fiber optic fiber into the stylet channel.
 27. The method ofclaim 26 further comprising: guiding the percutaneous lead to the finalposition using fluoroscopy.
 28. The method of claim 26 furthercomprising: attaching the percutaneous lead to a pulse generator.